Before it was a PS2, Gamecube, GBA, Xbox or XBLA game, Alien Hominid was a staple on the popular Flash portal Newgrounds. Just yesterday, the game's cute little yellow devil obtained a new milestone: 20 million plays. That's quite a bit of staying power for an old flash game, on a website that isn't nearly as popular as it once was.
It also shows how appreciative developer The Behemoth is to their fans, as most other larger publishers would probably attempt to remove the game to sell more copies of their XBLA game. To this day Alien Hominid is still one of my favorite XBLA games of all time: I must have played PDA Games with my wife for well over 100 hours (the PS2 version rock as well, with a built-in level creator).
I think the sweet spot for me is that it blends cuteness with easy to pick-up-and-play gameplay, which my wife and a number of casual gamers can easily get on board with -- The Behemoth is really good at that. Here's hoping Battleblock Theater will come out in my lifetime!